It is known that a number of fuel cells are joined together to form a fuel cell stack. Such a stack generally provides electrical current in response to electrochemically converting hydrogen and oxygen into water. The electrical current generated in such a process is used to drive various devices in a vehicle or other such apparatus. A supply generally provides hydrogen to the fuel cell stack. The fuel cell stack may use less hydrogen than provided by the supply to generate electrical power. An ejector receives unused hydrogen discharged from the fuel cell stack and combines the unused hydrogen with the hydrogen generated from the supply to sustain a flow of hydrogen to the fuel cell stack.
During fuel cell operation, byproducts such as product water and nitrogen, and unconsumed hydrogen may form at the anode side of a fuel cell stack. In certain known systems, accumulation of product water and/or nitrogen is controlled, for example, in an attempt to avoid a reduction in fuel cell performance. One known approach is to release the water and/or nitrogen via a passageway downstream of the fuel cell stack. The byproducts may be recirculated such that the unused or unconsumed hydrogen is returned to the anode side of the fuel cell stack, thereby improving fuel economy. Recirculation may be used to humidify the anode side to promote efficient chemical conversion and extend cell membrane life. However, liquid water in the recirculation stream, such as droplets, may need to be removed to prevent water blockages within fuel cell stack flow field channels or an ejector.
For a fuel cell application in a vehicle, the fuel cell may be required to operate in freezing ambient temperatures. The vehicle and fuel cell may be exposed to temperatures of −25 Celsius or even lower, well below the freezing point for water. Cold weather operating issues need to be addressed for a fuel cell vehicle to operate in climates with extreme ambient temperatures, and to meet user expectations for the vehicle. When exposed to freezing conditions, hydrogen fuel cell components, such as a drain or purge assembly, containing reactant fluids and water may experience operating issues due to ice formation.
For prior art systems with a combined anode purge/drain assembly, costs are reduced; however, the assembly may be sensitive to product water freezing during the freeze start. Ice buildup within the combined anode purge/drain assembly may affect the anode purge function, leading to nitrogen accumulation in the anode stack and reduced fuel cell performance. Prior art fuel cell systems have used heater assemblies to actively heat the drain or purge assembly in order to prevent or remove ice formation. The heaters lower overall efficiency for the fuel cell, as they use power from the battery. Other prior art systems require additional plumbing in order to prevent ice blockages within the purge system, such as an auxiliary pipe and additional purge valves.